Mayor Mitch Landrieu said Tuesday that four helicopters will begin attacking a marsh fire in eastern New Orleans today by dropping baskets of water on the smoldering acreage. Landrieu said another five helicopters are expected to join the firefight on Wednesday.

The UH-60 Blackhawk helicopters are equipped with Bambi buckets and will start dropping water at a site about 500 yards from the main fire, according to the mayor and the National Guard.

"There is a spot that I believe and other experts believe started separately, smaller, and with a potential to spread," Landrieu said at a 3 p.m. press conference. "We will go get that first and then move back to the other 2,300 acres."

Each helicopter can carry about 500 gallons and will only drop water during daylight hours for safety reasons. More could be added in the coming days if needed, Landrieu said.

Acrid smoke from the stubborn marsh fire that has burned at least 2,300 acres of swampy ground in eastern New Orleans -- an area two and a half times the size of City Park -- blanketed downtown New Orleans this morning, prompting a renewal of warnings from health professionals and restrictions on local school students' outdoor activities. The Louisiana Department of Environmental Quality renewed an Air Quality Alert today for the area south and southwest of Lake Pontchartrain because of the high levels of particulate matter in the smoke.

The decision to dump water from the air came less than 24 hours after Landrieu and his top aides insisted that such a response wouldn't extinguish the fire any more quickly than simply letting it burn itself out, an eventuality officials predicted would take no longer than three days.

Fire Superintendent Charles Parent during a Monday afternoon news conference said, "After consulting with our partners on the state and federal level, we feel that a water drop would probably be ineffective at this time because of the large size of the fire."

But criticism of the official response has mounted, particularly when it comes to Landrieu, who is slated to host a long-planned community meeting this evening in eastern New Orleans.

When asked why the helicopters are only being used now, Landrieu said, "All I can tell you is this particular land, because it is swamp and because it is wet, is not expected to have equipment on it to allow you to fight a fire as if it were across the street at the Hyatt Regency or elsewhere."

Bret Lane with the Louisiana Department of Agriculture and Forestry said fighting a fire like this has proved difficult. "Early in the year, we had one that burned for 3 1/2 months in Lake Bisteneau" in the northwestern part of the state, Lane said. "Once it goes underground, it's impossible to fight, because you can't bring enough water to it to reach it underground."

Shifting winds moved the the fire's smoke plume into northern Plaquemines Parish early today and now is pushing it west into Jefferson and St. Charles parishes, according to the National Weather Service.

Later today, the winds will shift again, pushing the smoke towards the northshore of Lake Pontchartrain, and there's little chance of the rain needed to put out the fire until Thursday morning, with more rainfall expected through the weekend, said Tim Erickson, a meteorologist with the Slidell office of the National Weather Service.

"It's like standing on the other side of a fire and the smoke seems to follow you," Erickson said. He said the fire has consumed 3,000 acres.

Early Tuesday Landrieu accompanied a Louisiana Department of Wildlife & Fisheries official and state Rep. Austin Badon, D-New Orleans, on a flyover of the fire, which is in an area about 1,500 yards to 2,000 yards north of Chef Menteur Highway and west of the Maxent Canal, which marks the western border of the Bayou Sauvage National Wildlife Refuge, and is entirely surrounded by water.

"This fire could not have happened in a worse place," Badon told WVUE-Channel 8 after the flyover. He said that while fire officials have said the blaze is too remote to reach, asking for federal help hasn't been ruled out. "We're going to reach out to the federal government to see if they can bring in assets."

Most of the brush is smoldering, he said. "The way we look at it, it should go on another five to seven days."

Badon said he and Landrieu saw a second fire near the main blaze while they were in the air, this one more suspicious since there has been no lightning to ignite it like the Fire Department thinks sparked the fire last week. "We think someone went out there and set that fire. ... Someone probably had to go out there and set it," he said.

Parent told WWL-AM this morning that he hopes to get firefighters onto the burn area with a marsh buggy to "get a better eyes-on view" of how deep into the organic soil the fire is burning.

"It's burning at a rapid rate, so we hope that even without rain, it consumes all the fuel," the organic material that is burning, Parent said. "If it consumes all the fuel, there will still be some smoldering and I may have to send my troops in to hit those little hot spots, but we'll have a better handle on it."

Gerald Herbert, The Associated PressThick smoke from a burning marsh fire in New Orleans East surrounds the Louisiana Superdome in downtown New Orleans, Tuesday, Aug. 30, 2011. Easterly winds kept a pall of smoke from the fire over the New Orleans area for the third straight day, and the National Weather Service issued a smoke alert for seven parishes.

Parent's comments were followed by a number of residents who called in to complain about the decision not to fight the fire more aggressively.

Erickson said slightly higher wind speeds on Wednesday could provide a bit of relief by stirring the smoke and moving it away from the city more quickly.

"We're going to get a mostly southerly wind even at midnight tonight, and we may get smoke over the Northshore by dark, so it's going to go around the whole compass," he said.

"By tomorrow morning, a light, easterly wind component will be moving the plume from east to west again and it will be in a straighter line as the winds pick up to 10 to 12 knots or so by late tomorrow afternoon."

The increased windspeed should mean that residents in St. John the Baptist Parish or even farther west will be able to smell the smoke tomorrow, but not at the intensity it hit the Central Business District this morning, Erickson said.

A low pressure system that is expected to move into the Gulf of Mexico on Thursday will be pushing to the north the high pressure ridge that's been trapping the smoke near ground level, and will deliver enough moist air to the area to spark rainfall.

"It will be the start of a little bit of a wet pattern lasting three or four days, depending on how strong the low develops," Erickson said.

The state environmental agency warned that smoke will continue to be a health issue for sensitive groups, including the elderly and people with asthma and other respiratory diseases. it urged people in those groups to avoid prolonged outdoor activites and exertion.

At City Park, a Department of Environmental Quality monitor registered 170.2 micrograms per cubic meter of 2.5 microgram or smaller particulates at 11 a.m., 199.1 micrograms per cubic meter at noon, and 135.3 micrograms per cubic meter at 1 p.m. The federal standard is an average over 8 hours of no more than 35 micrograms per cubic meter.

The threat of the smoke to people with pre-existing heart and lung disease is especially acute, said Dr. James Diaz, director of the environmental and occupational health sciences program at the Louisiana State University School of Public Health, in an interview Monday.

"It's very irritating to the airways and mucous membranes of the eye and nose, and the upper respiratory tract," Diaz said. "It can cause bronchospasms and asthma attacks."

He said those exercising outdoors, particularly joggers and swimmers are more at risk because the intense activity increases the rate of breathing, and inhalation of the tiny particles.

"The best thing to do is shelter indoors in any sort of area with good air filters," he said.

At West Jefferson Medical Center, emergency personnel treated two non-critical patients with respiratory complaints attributed to the smoke, one on Monday and another today. By noon today, Tulane Medical Center reported 25 patients had complained of effects from the smoke.